Embodiments of the present invention relate broadly to seating units designed to support a user's body in an essentially seated disposition. Commonly, seating units include a backrest and/or a seat that are constructed with a hardness or firmness which is invariable. By way of example, springs or coils that provide structure for a seat or a backrest of an automotive-style of seating unit will support an occupant within a specific hardness or firmness. This hardness or firmness is fixed because it is based on permanent characteristics (e.g., flexure, thickness, wind diameter, material traits) of the springs or coils. Accordingly, various occupants of the seating unit (e.g., operators of the vehicle) with individualized preferences of hardness or firmness will likely experience discomfort when sitting in the seating unit for a period of time.
Consequently, integrating an apparatus into seating units to allow for user-initiated control of the firmness of portion(s) of a seating unit would enhance the user's experience (e.g., level of comfort or support) when occupying the seating unit. Accordingly, embodiments of the present invention pertain to a novel adjustable foundation that is configured to increase or decrease the longitudinal tension in one or more extensible supports that span the adjustable foundation, where the longitudinal tension may be adjusted to achieve a level of firmness within the seating unit based on an indication provided by an occupant thereof.